A Cochrane review (abstract , review [Abstract]) included 5 studies with a total of 113 subjects. Participants in 4 studies had mild to moderate asthma and the fifth study included participants independent of their asthma severity. There were substantial differences between the studies, including the training protocol, duration of training sessions (10 to 30 minutes) and duration of the intervention (3 to 25 weeks). The included studies showed a statistically significant increase in inspiratory muscle strength, measured by maximal inspiratory pressure (PImax) (MD 13.34 cmH2O, 95% CI 4.70 to 21.98, 4 studies, n=84). Exacerbations requiring a course of oral or inhaled corticosteroids or emergency department visits was not reported. Results from one study showed no statistically significant difference between the inspiratory muscle training group and the control group for maximal expiratory pressure, peak expiratory flow rate, forced expiratory volume in one second, forced vital capacity, sensation of dyspnoea and use of beta2-agonist. There were no studies describing inspiratory muscle endurance, hospital admissions or days off work or school.
Comment: The quality of evidence is downgraded by study limitations (unclear allocation concealment), by inconsistency (variability in results), and by imprecise results (few patients).
Primary/Secondary Keywords